Conventionally, a vehicle driving operation assisting device which assists a driving operation of a driver in a longitudinal direction and a lateral direction is known. This vehicle driving operation assisting device detects an obstruction with respect to a driver's vehicle, calculates a degree of risk of the driver's vehicle with respect to the obstruction, and controls the operation of the vehicle equipment in order to encourage the driver to drive in the lateral direction and the longitudinal direction based on the degree of risk (Japanese Patent Application Laid-open (JP-A) No. 2003-327018).
Further, a target composite force applied to a vehicle body is calculated, a size of a critical friction circle of each wheel is estimated, a critical composite force is estimated based on the size of the estimated critical friction circle, a ratio between the target composite force and the critical composite force is set as a μ-utilization ratio, the magnitude of a tire generating force is set based on the size of the critical friction circle and the μ-utilization ratio, the direction of the tire generating force generated in each wheel to be controlled is set, and the steering operation, the braking operation and the driving operation are controlled in coordination based on the magnitude of the set tire generating force and the set direction of the tire generating force (JP-A No. 2004-249971).